This invention relates, in general, to semiconductor devices, and more particularly to the fabrication of CMOS devices which may be integrated into a BICMOS process.
A major trend in the semiconductor art is towards the fabrication of circuits integrating devices of multiple technologies. For example, a BICMOS integrated circuit which contains both bipolar and CMOS devices is highly desirable because the best characteristics of both technologies may be obtained and superior high performance integrated circuits may be fabricated.
There have been many problems associated with the integration of bipolar and CMOS devices into a single circuit. It is generally impractical to fabricate CMOS devices in a traditionally bipolar structure and vice versa. Many attempts at doing so have resulted in circuits having poor performance and requiring large amounts of real estate. Accordingly, the practical fabrication of BICMOS integrated circuits must have process integration flexibility as well as enhanced scalability characteristics.
In view of the above, it would be highly desirable to have a method of fabricating a CMOS structure that could be easily integrated into a BICMOS process.